Or is it both tlt attacks have to miss then the cruise triggers?

Both attacks have to miss per the timing chart.

Per the timing chart, you don't trigger "after attacking" abilities between the first and second attacks of a PTAT* weapon.

Per the clarification on Gunner, for a PTAT attack to count as having missed, both of its attacks must miss.

*: Perform This Attack Twice

At least now for things like TLT or Cluster Missiles to "miss" they have to completely miss with both attacks.

Correct, anything that says "Perform this ATTACK Twice," both shots have to miss to trigger a "miss" effect.